The technology disclosed herein generally relates to systems and methods for controlling an airplane to achieve desired performance and, more particularly, relates to systems and methods for enhancing the performance of an airplane during takeoff.
Takeoff is a phase of flight when an airplane transitions from moving along the ground to flying in the air. An airplane may make this transition when a takeoff speed is reached. The takeoff speed for an airplane may vary based on a number of factors. These factors include, for example, air density, airplane gross weight, airplane configuration, runway conditions and other suitable factors. A typical takeoff distance (referred to by a pilot) may be based on the assumption that all runway surfaces are paved, level, smooth and dry. However, in reality runway surfaces differ as does the runway gradient or slope (i.e., the change in runway height over a length of runway, expressed as a percentage). In addition, the pilot should consider the gross weight of the airplane when predicting takeoff distance (a.k.a. takeoff roll). An increase in gross weight may have the following effects on takeoff performance: (1) higher lift-off speed; (2) greater mass to accelerate; and (3) increased drag and ground friction. Furthermore, the speed needed for a takeoff is relative to the motion of the air. For example, a headwind reduces and a tailwind increases the groundspeed at the point of takeoff. Accordingly, the effect of wind must also be considered when predicting takeoff distance. The density altitude also affects takeoff performance. Density altitude is determined by first finding the pressure altitude and then correcting this altitude for nonstandard temperature variations. Using a flight computer, density altitude can be computed by inputting the pressure altitude and outside air temperature. As the density of the air increases (lower density altitude), airplane performance increases.
Information regarding the factors affecting takeoff performance may be incorporated in charts to which a pilot can refer. Takeoff distance charts are typically provided in several forms and allow a pilot to compute the takeoff distance of the airplane with no flaps or with a specific flap configuration. The typical takeoff distance chart provides for various airplane weights, altitudes, temperatures, winds, and obstacle heights.
Various segments of the takeoff flight path are specified in Part 25 of the Federal Aviation Regulations. In accordance with those specifications, during the first segment of the takeoff flight path, the airplane steadily increases its speed from zero to the minimum takeoff safety speed V2. During that first segment, the airplane first reaches the takeoff decision speed V1 and then reaches the rotation speed VR, before reaching the minimum takeoff safety speed V2.
A known operations technique for improving climb takeoff uses excess field length to increase the climb energy and, as consequence, increase the gross gradients for the various takeoff segments. In accordance with this procedure, this is achieved by increasing the rotation speed VR and the takeoff safety speed V2 by a certain amount, which corresponds to increasing the takeoff distance, or whenever VR reaches the tire speed rating. Although the rotation speed VR and takeoff safety speed V2 are modified, the initial pitch angle target is fixed and the same as the one used in the regular takeoff technique.